This dissertation examines how grammatical knowledge and referential salience guide early world learning in autism, a developmental disability characterized by significant language deficits. The process of word learning requires a child to match co-occurrences of words of parts of words (morphemes) and their meanings. This matching demands the integration of multiple, probabilistic cues from the linguistic, social, and real-world contexts, and thus may depend on working memory. Paradoxically, the limited short-term verbal memory characteristic of typically-developing children may improve this analysis of co- occurrences. Their limited memory for verbal strings may focus attention on smaller elements, which in language are the most important meaning- bearing units for grammatical information. In contrast, a pattern of efficient verbal short-term memory and limited working memory could impede rule-learning, leading to language delays. This pattern is thought to characterize children with autism, and thus may help explain their language deficits. The present study examines early language in autism using a word-learning task that varies both grammatical and referential cues to a novel word. This task, which examine sub-categorization into count and mass non classes, is highly relevant to word learning in normal development. The influence of social and non-social referential cues is also compared. Working and short-term phonological memory are tested in order to assess whether the hypothesized pattern of memory deficits is correlated with performance on the lexical task. Participants will be 20 children with autism, 20 verbal and chronological age-matched children with Down syndrome, and 20 verbal mental age-matched normal controls. Results will inform out understanding of language development in autism and thus have important implications for intervention. Results will also heighten our understanding of the roles that working and short-term phonological memory play in language development.